In recent years, with the expansion of the recording capacity of magnetic disk devices, the density of recording with a magnetic head onto a recording medium has been increased. For this reason, it is important to increase positioning accuracy of the magnetic head when data is written onto the recording medium.
For positioning of the magnetic head on a track of a magnetic disk, the VCM is generally used. The VCM includes an electromagnetic coil (hereinafter, referred to as “VCM coil”). By using the VCM coil, a revolving arm is controlled so that a magnetic head at the tip of the revolving arm is moved to a target position on a track.
When this movement of the magnetic head continues, it is known that the VCM coil is so heated by an electrical signal transferring through a wire material that the temperature of the VCM coil exceeds its heat-resistant temperature, becoming unable to keep its shape as a coil to possible malfunction.
To get around this problem, a technology is disclosed in which a component that lets an airflow pass toward the VCM coil is provided to supply an airflow occurring by the rotation of the magnetic disk to the VCM coil, thereby cooling the VCM coil.
Meanwhile, it is known that, when a VCM coil is used to move the magnetic head, blowing air on the VCM coil decreases accuracy of positioning the magnetic head at a target point on a track.
To get around this problem, in a disclosed example of configuration of the magnetic disk device, an airway is provided along the outer wall of a housing that covers the magnetic disk to let an airflow occurring over the disk surface by the rotation of the magnetic disk flow through the airway, thereby preventing air from blowing onto the VCM coil. Such conventional technologies are also exemplarily disclosed in Japanese Laid-open Patent Publication No. 2000-156068 and Japanese Laid-open Patent Publication No. 11-110960.
However, preventing air from blowing onto the VCM coil may disadvantageously cause a malfunction of the magnetic disk device due to an increase in temperature.
Thus, in a conventional technology of blowing air onto the VCM coil for cooling so as to prevent an increase in temperature of the VCM coil, an airflow occurring by the rotation of the magnetic disk is always supplied to the VCM coil. Therefore, even when it is not necessary to cool the VCM coil, the supplied airflow rocks the VCM coil, thereby possibly decreasing positioning accuracy of the magnetic head. In particular, when the rotation speed of the magnetic disk is set high, the airflow speed is also high, thereby causing the VCM coil to be rocked strongly and further decreasing positioning accuracy of the magnetic head. Moreover, when the magnetic disk device is downsized, the rocking of the VCM coil is relatively increased, thereby possibly causing a significant decrease in positioning accuracy of the magnetic head.
According to the configuration of the recording-medium driving device of the present invention, when the temperature of the control unit exceeds the limit value defined in advance, the temperature of the control unit can be decreased by using the guided airflow, thereby cooling the control unit as required. As a result, it is possible to prevent a malfunction of the recording-medium driving device due to an increase in temperature of the control unit. Also, in the recording-medium driving device according to the present invention, when the temperature of the control unit does not exceed the limit value defined in advance, the airflow toward the control unit is cut off, thereby preventing the rocking of the control unit and increasing overall accuracy of positioning the magnetic head.